The beam shaper/projection unit may be employed when generating any structured illumination in many fields of application, like background and accentuating illumination in general illumination, generating defined radiation profiles for automobile applications, generating light patterns on objects for measuring purposes, for example. Information can be visualized optically, wherein this may be done both by illuminating a real target and by generating virtual images visible to the eye.
In order to be able to objectively perform a comparison between different solution approaches, some relevant characterizing quantities of such beam shapers/projection units will be summarized below briefly. The following characterizing quantities are relevant for most applications in illumination and projection tasks:
(A) ensuring a sufficiently large light flux/optical power
(B) compact, miniaturized optics, wherein the main emphasis is placed on the optics thickness
(C) high power transmission through the optics/power efficiency
(D) way of generating most different light distributions:
                coarse, smooth, weakly varying distributions        fine, highly patterned light distribution with high a resolution, like in writings, for example, high-resolution images        range from little contrast up to very high contrasts (like target regions within the illumination range with no light)        any edge geometries        most different requirements in combination(E) homogenization effect relative to spatial source inhomogeneity, in particular way of color mixing, sufficient tolerances, particularly relative to source location and source arrangement        
(i) Patterned illumination and projection of light distributions having single-channel macroscopic projectors are well-known [Malacara]. Any desired light distributions (D) on targets can be generated. However, light is faded out by absorptive slides or dynamics imagers, for example, which may result in a considerable loss in power efficiency (C). Usually, the Köhler illumination principle will be applied, which means transforming the source spatial domain to the target ray domain (E), but further light mixing has to be introduced specifically, like by using honeycomb condensers [Pan]. When miniaturizing (B), i.e. reducing optics height, of single-channel projectors [Pan, US 2006/0285078 A1], the optics area or surface has to be reduced at the same time, which entails a reduction in the transmissible light flux (A).
(ii) For generating any desired patterned illumination pattern of very high power efficiency (C), refractive or reflective illumination free-forms can be used [Ries, Oliker]. This kind of free-form illumination is based on a refractive or reflective light redistribution and principally does not need any absorptive or fading structures. Usually, the source light is transferred to the target with no additional projection unit. Generating strip patterns for measuring purposes is to be mentioned as an example of application [DE 102011014779 A1]. However, applying this type of free-form redistribution exhibits considerable deficiencies. In light redistribution, the light distribution impinging on the free-form/free-forms (i.e. the source distribution or the source distribution modified by primary optics) has to be well-known and may not be subjected to changes, which means that the system is relatively intolerant (E). Homogenization and light mixing effects and Köhler illumination etc. are not present in this case. In analogy to the macroprojector as described above, the miniaturization and light flux problem applies here, too (A, B). However, the by large greatest deficiency is the limited resolution in light distribution generation for realistic source distributions [Zwick]. Very fine light distribution patterns on the target can only be generated if the source distribution can be described approximately as a wave front, i.e. with very well collimated source radiation or very small a source area, for example. Otherwise, the result will be relatively strong blurring or smearing effects which have to be taken into consideration in optical design on the one hand [Wu] and prevent fine target patterns on the other hand. For this reason, the most frequent practical application of redistribution free-forms is generating very smooth or homogenous illumination [Luo, Wu, Zhao].
(iii) When connecting projection and free-form optics, two trends can be observed basically. On the one hand, redistribution free-forms as described above are used for good homogenous illumination of slides or imagers or light mixers [Zhao, Minano]. On the other hand, imaging free-forms, i.e. free-form elements in the optical illumination path of the projector, may result in more compact optics of higher imaging quality [Rico, U.S. Pat. No. 8,717,671 B2, U.S. Pat. No. 8,616,711, US 2015/0205099 A1]. However, the deficiencies as described in (i) are not decreased by this.
(iv) The deficiency of low a light flux as described under (i), i.e. the low brightness on the target, when reducing the optics height, has been eliminated by so-called array projectors [DE 102009024894 A1, DE 102011076083 A1, Sieler]. By using a plurality of optical channels having at least one condenser lenslet, an object pattern to be imaged and at least one projection lenslet per optical channel, the optics height is reduced and high a light flux is ensured as well. Homogenization and light mixture effect, the Köhler illumination principle and tolerances relative to source distributions can be found here. However, the problem of a potentially low power efficiency or system transmission is still present. By absorbing or fading light as a consequence of object patterns to be imaged, considerable transmission losses may arise. Considerable losses result, for example, when generating grey scale profiles having strong irradiation intensity maximums, when forming narrow light pattern features on a less bright or even lacking background illumination or when generating non-trivial boundaries of the real or virtual region to be illuminated.
Well-known single-channel projectors or illumination configurations consequently exhibit the disadvantages that a miniaturization of the projectors/illumination configurations entails a reduction of the light flux transmissible. In addition, current illumination configurations having free-form light redistribution with real input light distributions exhibit considerable deficiencies and can be used exclusively with nearly collimated input light or small source areas for generating spatially high-frequency illumination patterns. Otherwise, the result may be relatively strong smearing or blurring effects so that no fine patterns can be generated in a projected image. In addition, such systems are optically intolerant. Furthermore, apertures in projectors may considerably reduce an input light flux of the projector, the result being strongly reduced power transmission.